What is the treatment for Enterococcus faecalis in urine using nitrofurantoin?

Nitrofurantoin for Enterococcus faecalis Urinary Tract Infections

Nitrofurantoin 100 mg orally every 6 hours for 5-7 days is an effective treatment option for uncomplicated urinary tract infections caused by Enterococcus faecalis, with excellent in vitro activity and low resistance rates below 6%. 1

First-Line Treatment Hierarchy

Preferred Agent: Ampicillin/Amoxicillin

• Ampicillin or amoxicillin remains the drug of choice for enterococcal UTIs, with amoxicillin 500 mg orally every 8 hours for 7 days achieving clinical cure rates of 88.1% and microbiological eradication rates of 86%. 1
• High urinary concentrations of ampicillin can overcome high MICs even in ampicillin-resistant strains, making it effective when in vitro testing suggests resistance. 1
• For hospitalized patients requiring IV therapy, use high-dose ampicillin 18-30 g IV daily in divided doses or amoxicillin 500 mg IV every 8 hours. 2, 1

Nitrofurantoin as Alternative

• Nitrofurantoin 100 mg orally every 6 hours for 5-7 days is recommended for uncomplicated UTIs due to E. faecalis, particularly when ampicillin cannot be used. 2, 1
• Nitrofurantoin demonstrates 88% susceptibility against enterococcal isolates, including both E. faecalis and E. faecium. 3
• This agent retains antimicrobial efficacy even against vancomycin-resistant enterococci (VRE), with 80.76% of VRE isolates remaining susceptible. 4
• No resistance to nitrofurantoin (MIC ≥128 μg/ml) was found in studies testing 300 enterococcal isolates, including vancomycin-resistant strains. 5

Other Alternatives

• Fosfomycin 3 g orally as a single dose is FDA-approved specifically for UTI caused by E. faecalis and is recommended for uncomplicated infections. 2, 1

Critical Clinical Considerations

Distinguish Infection from Colonization

• Always differentiate true infection from asymptomatic colonization before initiating therapy, as asymptomatic bacteriuria with E. faecalis does not routinely require treatment. 2, 1
• Obtain urine culture and susceptibility testing before initiating therapy, even for strains described as "pansensitive," as resistance patterns vary significantly by institution. 1

When to Use Nitrofurantoin

• Use for uncomplicated lower urinary tract infections only (cystitis). 2
• Do not use nitrofurantoin for pyelonephritis or complicated UTIs requiring systemic therapy, as it achieves inadequate tissue concentrations outside the urinary tract. 2
• Appropriate for patients with penicillin allergy who cannot receive ampicillin/amoxicillin. 1

Dosing Specifications

• The 2022 guidelines recommend nitrofurantoin 100 mg orally every 6 hours (four times daily). 2, 1
• The 2024 European guidelines suggest alternative dosing of 50-100 mg four times daily for 5 days or 100 mg twice daily for 5 days. 2
• Treatment duration should be 5-7 days based on clinical response. 2, 1

Common Pitfalls to Avoid

• Avoid fluoroquinolones due to high resistance rates (46-47% for ciprofloxacin/levofloxacin) and unfavorable risk-benefit ratios for uncomplicated UTIs. 1
• Do not use nitrofurantoin for systemic enterococcal infections (bacteremia, endocarditis, intra-abdominal infections) due to inadequate serum levels. 2
• Do not perform routine post-treatment urine cultures in asymptomatic patients. 2
• For symptoms that do not resolve or recur within 2-4 weeks, obtain repeat culture and assume the organism is not susceptible to the original agent. 2

Special Populations

Vancomycin-Resistant Enterococcus (VRE)

• Nitrofurantoin maintains excellent activity against VRE in urinary tract infections, with 80-88% of VRE isolates remaining susceptible. 4, 3
• Among strains resistant to ampicillin, vancomycin, and other agents, 50-88% remain susceptible to nitrofurantoin. 3

Pregnancy

• Nitrofurantoin has a continuing safety record spanning over 35 years and lacks R-factor resistance development. 6
• It has been used safely for treatment of asymptomatic bacteriuria of pregnancy. 6